98 research outputs found
Destruction plasmachimique dâurĂ©e et de thiourĂ©e par dĂ©charge Ă©lectrique Ă pression atmosphĂ©rique
Le traitement Ă la pression atmosphĂ©rique de solutions aqueuses dâurĂ©e et de thiourĂ©e par plasma dâarc rampant en atmosphĂšre dâair humide conduit Ă la dĂ©gradation totale de ces composĂ©s. Les cinĂ©tiques globales dâordre nul ont des constantes voisines proches de 3âą10â6 sâ1. Le procĂ©dĂ© met en jeu les espĂšces actives crĂ©Ă©es dans la dĂ©charge, les radicaux OH et NO, responsables des caractĂšres chimiques principaux du plasma : oxydation du fait de la prĂ©sence de OH (E°OH H2O = 2,85 V/ENH) et acidification, provenant de la formation dâacides nitreux et nitrique en solution. Ces rĂ©sultats sont relatifs Ă des molĂ©cules modĂšles, mais suggĂšrent lâextension du procĂ©dĂ© Ă la dĂ©gradation de molĂ©cules toxiques et dâeffluents industriels soufrĂ©s.Electric discharges in humid air (i.e., a gliding arc discharge at atmospheric pressure and quasi-ambient temperature) are considered in the context of evaluating new techniques for pollution abatement. An electric discharge in a gas under specific conditions gives rise to a plasma, which involves activated gas species with enhanced reactivity. The main chemical properties of a discharge in humid air are attributed to NO and OH radicals formed in the discharge, which are able to react with solutes at the plasma/liquid interface. These activated species are formed in advanced oxidation processes and are respectively responsible for acid and oxidizing effects in the target solution: NO gives rise to nitrous and nitric acids, and OH is strongly oxidising [E°(OH/H2O) = 2.85 V/NHE].To examine the degradation power of the plasma treatment on molecules of the same family and to evaluate the ability of the gliding arc system to oxidize sulphur-containing solutes (2 x 10â3 M) in batch conditions, aqueous urea and thiourea were selected as suitable target solutions. The solutes were completely degraded within 180â200 minutes of treatment and the concentrations decreased linearly with increasing exposure times in the discharge. This trend accounts for overall zero-order kinetic schemes with the relevant rate constants of kurea = 5.28 x 10â6 sâ1 and kthiourea = 2.03 x 10â6 sâ1.The evolution of solutes with time was followed by total organic carbon (TOC) measurements for urea, and by the conductometric titration of the sulphate ions formed in the case of thiourea. Spectrophotometric measurements of the treated solutions at the solute absorption peaks were found to be unsuitable for analysis purposes due to the formation of nitrite/nitrate ions which absorb in the same wavelength range.The extension of a gliding arc system from the laboratory level to an industrial scale for pollution abatement of industrial effluents is considered
Understanding plasma-ethanol non-equilibrium electrochemistry during the synthesis of metal oxide quantum dots
Plasmaâliquid interactions are becoming increasingly interesting due to their key features such as non-faradaic, non-equilibrium behaviour as well as electron-driven reactions, therefore with potential strong impact for several promising applications. However, understanding reaction mechanisms initiated at the plasmaâliquid interface is complicated by short timescales and spatial non-uniformities. Here we study a plasmaâethanol system that has general relevance to broaden our understanding of plasma interacting at the surface of a liquid. This plasma-electrochemical approach has been successfully used to synthesize a range of metalâoxide nanoparticles and quantum dots (QDs). While nanoparticles and QDs can be an end to this process, they can also be viewed as âchemical probesâ that help understanding the underlying and progenitor chemical reactions. We have therefore studied plasmaâethanol interactions during the synthesis of CuO QDs. The colloid was characterised by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. Further, measurements for pH and other trace products were also carried out. The analysis shows the acidolysis of the ethanol electrolyte where hydrogen peroxide was found after the plasma process. A semi-quantification of Cu ions was carried out to confirm the anodic dissolution of the Cu metal foil. Thus, a detailed set of reactions are proposed and has been discussed in detail. Material characterisation relied on transmission electron microscopy and X-ray photoelectron spectroscopy which provided important and complementary information to corroborate chemical reaction paths
A plea for equitable global access to COVIDâ19 diagnostics, vaccination and therapy: The NeuroCOVIDâ19 Task Force of the European Academy of Neurology
Coronavirus disease 2019 (COVIDâ19), a multiâorgan disease caused by severe acute respiratory syndrome coronavirus 2 (SARSâCoVâ2), continues to challenge health and care systems around the globe. The pandemic has disrupted acute neurology services and routine patient care and has impacted the clinical course in patients with chronic neurological disease. COVIDâ19 appears to have exposed inequalities of societies and healthcare systems and had a disproportionate impact on already vulnerable communities. The next challenge will be to set up initiatives to stop disparities in all aspects related to COVIDâ19. From the medical perspective, there is a need to consider inequalities in prevention, treatment and longâterm consequences. Some of the issues of direct relevance to neurologists are summarised. With this appraisal, the European Academy of Neurology NeuroCOVIDâ19 Task Force intends to raise awareness of the potential impact of COVIDâ19 on inequalities in healthcare and calls for action to prevent disparity at individual, national and supranational levels
Catalytic non-thermal plasma reactor for mineralization of endosulfan in aqueous medium: A green approach for the treatment of pesticide contaminated water
The study of an electric spark for igniting a fuel mixture
Communication orale (B.Hnatiuc)International audienc
Electrical and Physical Properties of a Gliding Arc
[Communication orale (B.Hnatiuc)]International audienc
Nonthermal Plasma Multi-Reactor Scale-Up Using Pulse Capacitive Power Supplies
The scale up of nonthermal plasma (NTP) reactors requires the simultaneous operation in parallel of a large number of units supplied from the same power supply. The present paper aims to demonstrate the feasibility of parallel operation of multiple mini-NTP reactors. In order to demonstrate the parallel operation of a large number of NTP reactors, three different types of power supplies are considered. In addition to the most simple and common solution, which involves the use of individual, independent power supply for each reactor (an ignition coil driven by a pulse generator), two other configurations of supplies (capacitive AC and capacitive DC), simpler and less expensive, are tested. The capacitive pulsed power supplies allow the generation of HV pulses by an AC power supply (usually an AC transformer), as well as by a DC power supply using an R–C circuit. For the DC resistive–capacitive configuration, the frequency can be adjusted. For all configurations, the power of the discharge can be modified by changing the value of capacitors or resistors. The feasibility of the proposed systems was demonstrated by assessing the concentration of hydrogen peroxide induced in water after plasma treatment. The obtained results reveal that the proposed capacitive AC and DC power supplies allow a large number of plasma reactors to operate in parallel independently
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